When a motor including a stator having a plurality of single-pole coils inserted in the slots of a stator core is to be manufactured, for example, it is necessary to form a coil as a plurality of continuous single-pole coils.
In the coil forming method of the prior art, a winder is used to form the single-pole coil by winding an electric wire around a stationary bobbin. In order to form another single-pole coil in continuity with the first single-pole coil thus obtained, the winder is turned in the opposite direction around the fixed bobbin, to form a single-pole coil having a reversed winding direction.
A coil forming method similar to the above-described method is disclosed in JP-A-2000-253631, for example. As described in JP-A-2000-253631, the external diameter of the bobbin for winding the electric wire can be changed, and a flyer (serving as the aforementioned winder) is turned around the bobbin. The wound single-pole coils are sequentially formed to produce the continuous-pole coil to be used in the motor.
However, the coil forming method of the prior art thus far described has the following problems. Specifically, the electric wire is fed while the winder is being turned, so that the wire is wound on the bobbin while being twisted by the turning motion of the winder. In the case where the coil is formed with the electric wire twisted, the occupation percentage of the coil is reduced for the reason that the electric wire cannot be individually moved into slots or that a dead space is formed by the twists.
The present invention has been conceived in view of the foregoing problems of the prior art and contemplates provision of a coil forming method and a coil forming apparatus which can form a single-pole coil without twisting the electric wire.